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A.C. FLETGHER. GRATE BAR.

No. 76,734. I Patented Apr. 14, 1868.

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Letters Patent No. (6,734, dated April 14, 1833; antedate'd April 3,1868.

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Be it known that I, Al DiOX C. FLETCHER, M. D., of. the city, county,and State of New York, have invented a certain new andusefullmprovenicnt in Grated-lure, of which the following is a-full,clear, and eiz'act description, reference beinghad to the accompanyingdrawing forming part of this specification, and in which- Figure 1'represents aii'ertical longitudinal section of a grate-bar constructedaccording to my improvement.

Figure 2, a vertical transverse section of the same, or a pair thereof,through the-line a: x in fig. 1; and

Figure 3, a plan of a few or series of such grate-bars arranged ineonnectiorfwithieach other.

Similar letters of reference indicate corresponding parts.

My invention has for its object the combustion, in a fireplace orfurnace, of'iniiammable gases in their escape to the chimney, by theintroduction of heated atmospheric air through perforations inn bridgeor rise in rear of the fuel, and the nature of my invention, in thisconnection, consists in a novel con'structiontof grsteharmprcferably ofa tubular character in direction of their length, and with a valve orvalves to control the admission of air at their outer ends, said orother suitable bars terminating in cylindrical formations, constituting,when the several bars are in their place, a transversebridge-liketubular structure, of a perforated character on its uppersurface, covered by a perforated coating offire-clay or brick-work,through which heated air, say, the air heated in its passage through thetubular grate-bars, escapes, to burn the carbonic oxide into carbonicacid, producing what may be termed a second burning in the furnace.

Referring to the accompanying drawing, A represents the longitudinalportion of the bars, preferably made double, so far as their tubularconstruction or arrangement of air-passages a a through them isconcerned, having open spaces 6 between the two portions of them,forming the double structure, and lugs or dividing projections 6 outsideof them, to team spuccs d between them and the adjoining bars. Theselongitudinal tubular portions A are providcd,at their outer ends, witha. valve or lid, or valves or'lids B, whereby atmospheric air may beexcluded from or admitted to, in a controllable manner, the passages aa, and said longitudinal portions A being furthermore constructed orprovided, and terminating in open communication with, at their innerends, transverse cyl-' inders G, of a bridge-like character relativelyto the longitudinal portions of the bars, and cast with or forming partof them, so that the insertion of the one portion in its place involvesor includes the proper arrangement and connection of the other. Thesecylinders C are arranged end by end, to form a continuous transversetubular bridge, and may be supplied with heated air from its end orends, but this may be unnecessary where "the longitudinal portion A ofthe bar is hollow, and air suppliedto the cylinders G by thepassages aa. In the upper surfaces of said cylinders C are perforations (Z, incommunication with apertures a, made in or through a fire-brick or'othersimilar covering, D. I I

On starting the fire, the lids or valves B should be closed, so as notto interfere with the draught, but after ignition -as been fairlyestablished or the fire in full blast, said lids areopened more or less,according to requirements, as regards the combustion of the gases, whichintroduces air through the passages a a, that, as it traversestheretbrough, is heated by the exterior exposure of the longitudinalportions A, on their upper surfaces andsides bound by the openings 6 d,and, entering the cylinders C, is further heated therein, as it emergestherefrom through the apertures d e, by reason of the location andcomparatively close construction of said cylinders and their fire-brickcovering D, which, being a slow conductor, serves to retain the heatcommunicated to it by the passage of theflamc and heated gases; over it.In this way is the air introduced to or over the fire at the hridgein ahighly-heated condition, producing a more perfect combustion of theescaping inflammable gases, the bridge and fire-bars proper, asrepresented in the drawing both contributing to this result, and bothformed of one or'the same piece, in the construction of the grate-bar orbars. 'loclean out said cylinders of matter lodging therein, the samemay be provided with lids or doors 8, or openings covered by lids ordoors, may he made in the brickwork, at the ends of the tubularstructure formed by said cylinders.

I do not claim a hollow grate-bar, nor a hollow perforated bridge, per8e; but

What I claim as my invention, and desire to secure by Lctters Patent,is-

1. A grate-bar, having cast to or forming part of it, in therear aperforated cylinder 0, having an gnnular projection on one side, and acorresponding recess on t he other, the aqial line of which cylindrisarranged transversely to the length of the her, the same forming, inconnection with the other bars pflihe construction. a. tubular pexforhted bridge, for the passage of heated air tq the fire,subsfianfially as specified.-

2. The application to a grate-bar, constructed subetantially asdescribed, of e'longitudinal tubular portion, A, terminating in a.transyerse cylindrical perforated structure, 0, ofbridge-likeeharacter,'and mogd to form part of the gr te-bar of an outside lici or halve, B, essentially es and for the purpose or purposesherein set forth.

ADDISON C. FLETCHER, M. D.

Witnesses:

A. LE (In-me, J. W. Commas.

